Elastic high-bulk yarn



June 12, 1962 c. R. HUMPHREYS 3,038,295 ELASTIC HIGH-BULK YARN Filed Dec. 24, 1958 FIGZ nited States Patent 3,fi38,295 Patented June 12, 1962 free 3,038,295 ELASTIC HIGH-BULK YARN Charles R. Humphreys, Wilmington, DeL, assignor to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware Filed Dec. 24, 1958, Ser. No. 782,744 14 Claims. (Cl. 57-152) This invention relates generally to the spinning of yarn and, more particularly, to a high-bulk elastic yarn produced by core-spinning a sheath of staple fibers about an elastic core.

As used herein, the term core-spinning refers to the process of introducing a continuous filament to a conventional spinning or drafting frame together with one or more rovings of staple fibers so that a composite yarn is formed in which the continuous filament is a core about which is spun a sheath of drafted staple fibers.

The presently, known elastic high-bulk yarns, such as Banlon and Helanca, are produced by crimping or twisting and setting, techniques... Despite satisfactory stretch characteristics, these yarns have a low retractive force.

Elastic yarns have also been produced by attaching a 7 multitude of parallelized fibers to a stretched rubber core. Each twist-free fiber is adhesively joined at two or more points in its length to the core so as to form biglits or loops when the core is relaxed. Although the resulting yarn is bulky, the process is complicated and requires special equipment for application of the adhesive.

In the past, rubber cores have been covered for a variety of reasons, among which are appearance, improved hand, protection of the rubber core against light, perspiration and grease, and to control the stretch ofthe composite elastic yarn. For example, the smooth elastic yarn known by the trademark Laton is produced by using a pre-twisted rubbe'r'core in a core-spinning process. Such rubber yarns have considerably higher retractive force than the Helanca type high-bulk yarns but, heretofore, a bulky yarn has not resulted from the use of a rubber core in, the process ofcore-spinning. Furthermore, the fact that rubber filaments are not commercially available in a denier less than about 300 imposes a rather severe limitation on the fineness of composite yarns having a rubber core.

It is the most important object of the present invention to provide an elastic'yarn of high bulk.

Another important object of the invention is the provision of a high-bulk, low denier elastic yarn according to a simple process which avoids the necessity of complicated and expensive procedures.

' Another object of the present invention is to provide a process for making high-bulk elastic yarns with convention'al spinning equipment.

With these and other objects in view, the low twist composite yarn of the present invention comprises gener-ally a stretched elastic core having a sheath consisting of one or more drafted rovings of staple fibers spun on the core with each roving surrounding the core in a series of helical turns in such a manner that, when the core is permitted to contract, the sheath fibers bulge outwardly to present a high-bulk yarn. The process for producing such a high-bulk yarn involves the steps of drafting at least one roving of staple fibers, tensioning an elastic core, entering the roving and the core at the nip of the front rolls of a spinning frame, and twisting the "roving and core under tension. When the critical factors of twist multiplier and core content are controlled within limits, the composite yarn resulting from the practice of this invention has both high-bulk and high retractive force. V Y

In the drawing:

FIGURE 1 is a schematic representation of a spinning frame modified according to the teachings of the present invention;

FIG. 2 is a schematic view, greatly enlarged, of yarn made in accordance with the invention, with the core 70% retracted from the stretched condition shown in FIG. 3; and

FIG. 3 is a view similar to FIG. 2, with the yarn shown extended.

Referring now to the drawings, the apparatus for carrying out the process of the invention has been illustrated schematically in FIG. 1. For purposes of clarity, line representations have been employed in FIGS. 2 and 3 to illustrate the elastic core and the sheath rovings of the composite core-spun yarn.

As shown in FIG. 1, rovings 10 are led from packages 12 through the back pair 13 of drafting rolls, and thence through intermediate pairs'14 to the front pair 15. A substantially twist-free, continuous elastic filament v16 passes through a tension device 18, over guide 24 and positioning guide 21 and, along with rovings 10, through the front rolls 15. The filament 16 which is illustrated in the drawing can be either a monofilament or a plurality of continuous filaments. From the rolls 15, the drafted rovings 10 and filament 16 travel through guide 22 to the traveler of ring twister 24. The operations in spinning are normal except that there must be sufiicient tension below the front rolls to maintain filament 16 at substantially the same percentage elongation below the front rolls as above. This is accomplished by the use of heavier travelers on ring twister 24 which function to maintain filament 16 in the stretched condition. The composite, core-spun yarn which is wound on bobbin 26 has filament 16 as a core and drafted rovings it) as a sheath. When the composite yarn is subsequently unwound from bobbin 26 and permitted to contract, the sheath fibers bulge outwardly in the form of loops or arches which impart resiliency and bulkiness to the yarn. As the amount of twist in the composite yarn is increased, the amount of sheath bulking decreases and is replaced by twist loops and kinks. Accordingly, a twist multiplier of less than about 4 is used and the composite yarn has a core content of less than about 40% by weight. By controlling these critical factors of twist multiplier and core content, elastic bulky core-spun yarns are simply and easily prepared on otherwise conventional equipment.

The term twist multiplier is a factor which relates the twist in turns per inch (t.p.i.) to the cotton count of yarn being spun. In cotton spinning systems, the formula used is:

T.p.i. =twist multiplier cotton count Converting this formula into units of denier,

Twist multiplier=% Unless otherwise specified herein, the term denier refers to the composite, elastic yarn in its fully stretched condition.

FIGURE 3 is a line representation of the stretched composite yarn as it is wound on bobbin 26. The two drafted rovings 10 of staple fibers have been spun about the elastic core 16 to form a sheath which substantially covers but is free of adhesion to the stretched core. As noted above, the bulkiness of the composite yarn arises when the core is permitted to contract. In the schematic representation of FIG. 2, the rovings 10 have been shown bunched by the contraction of core 16. In actuality, this contraction of the core also causes the individual, low

twist, non'elastic sheath fibers to bulge outwardly in the form of loops or arches (not shown). These loops or arches impart resiliency and bulkiness to the composite yarn.

Although an elastic yarn of suitable bulk is obtained when the core 16 is made of rubber, certain inherent disadvantages are involved, such as the fact that rubber filaments are not available in deniers finer than about 300 in the relaxed state. Additionally, rubber filaments are generally lacking in uniformity, cannot be dyed, and are adversely affected by sunlight, perspiration, grease and oils. When rubber is used and the dyed composite yarn is stretched, grinning occurs, i.e., the rubber core shows through the sheath. If extenuation is carried to the point where the sheath fibers bear the majority of the load, the core-spun yarn turns inside out with the rubber wrapped around the sheath fibers. In order to avoid these inherent difficulties, it is preferable to use as the core a segmented elastomer in monofilament form. By the term segmented elastomer is meant a polymer made up of segments of a high-melting, crystalline polymer alternating with segments of a low-melting, amorphous polymer.

A wide variety of suitable segmented elastomers exists.

excess of 4.0, there is some sheath bulking as the composite yarn is permitted to contract but the amount of bulking is not sutficient to classify the yarn as having high-bulk characteristics. The same is true for a yarn spun using a low-twist multiplier and having a core content in excess of 40%. Where the twist multipler is substantially in excess of 4.0, twist loops or kinks appear when the composite yarn is permitted to contract, as disclosed in detail in my copending application Ser. No. 782,742, filed December 24, 1958.

The process does not require that the elastic core be twisted prior to the spinning operation. However, if desired, the core may be pre-twisted as in the production of commercially smooth core-spun yarns (see Example 6 in the table which follows. If a pre-twisted core is used, the twist imparted during the spinning should be applied in the opposite direction.

The table which follows is a compilation of the comparative data for several composite yarns, all of which were produced on conventional spinning frames. It should be noted in advance that the smooth yarn of Example 5 was spun using a twist multiplier of more than four and a core content of more than 40%.

Sheath Composite Yarn Core- Example Original N0. Denier Cotton Twist Per- Denier Denier Fiber Staple Length Count or I.p.i Multlcent Ex- Relaxed Denier plier Gore tended 70 Polyacrylonitrile 38.7/1 3.4 17.4 157 485 d 38. 7/1 20 3. 8 29. 8 194 411 39/1 20 3. 8 37. 5 195 542 39/1 20 3. 8 32 198 661 39/1 20 4. 4 42 268 579 148 do 46. 4/1 14 2.4 158 474 150 Polyethylene terephthalate/ /1 17.75 3.0 14.4 155 365 wool (/45). Polyaerylonitrile 2/ 139/1 35.9 3.4 28.6 49 167 40 Cotton /1 38.4 3.7 20 49 148 200 Polyethyleneterephthalate. 30/1 16 3.7 37 291 398 423 Cotton CombedSupima 25/1 13 3.2 31.1 311 1,010 518 do d0 25/1 13 3.4 34.1 365 1,620

The crystalline, high-melting segment may be derived from a urea polymer, urethane polymer, amide polymer, bis-ureylene polymer, or polyester, for example. The low-melting, amorphous segment may be derived from an ester polymer, an ether polymer, or a hydrocarbon polymer, for example. Segmented elastomers of this type together with a process for obtaining them in filamentary form are described in US. Patents Nos. 2,813,775 and 2,813,776. Suitable polyether-polyester segmented elastomers are described in British Patent No. 779,054. The preferred segmented elastomers are those containing a bis-ureylene segment alternating with segments of a lowmelting polyether or polyester, as disclosed in copending application Ser. No. 556,071, filed December 29, 1955, now US. Patent No. 2,957,852.

Any textile fiber available in staple form may be used as the sheath fiber for spinning around the elastic core. Such fibers include the natural fibers cotton and wool, and the synthetic fibers rayon staple, nylon staple, polyacrylonitrile staple, polyethylene terephthalate staple, etc. Any staple length which is operable for the conventional process of ring-spinning is suitable. Twist multipliers in the range of about 2.0 to about 4.0 and preferably less than 3.7 are used in the practice of the present invention. Greater bulkiness is achieved by the use of low-twist multipliers. The properties of the core-spun bulky elastic yarns of the present invention are determined not only by the twist multiplier used but also by the percent of core elastomer present. Although percentages up to 40% have been used, preferably less than 30% by weight of elastomer core is present.

When the composite yarn has an extremely low core content and is spun using a twist multiplier slightly in In all except Examples 10 and 12, the preferred poly- (bis-uzreylene/ether) segmented elastomer was used as the core material. In Example 10, a poly(ester/ether) segmented elastomer was used. The core material in Example 12 was Parflex, an extruded rubber filament made from natural rubber latex by the Parfiex Rubber Thread Corporation of Providence, Rhode Island. In Example 6, the core had a pre-twist of 76 t.p.i.; in all other examples, the core was initially twist-free. With the exception of Example 5, each yarn exhibited highbulk characteristics. The tensile force required to stretch the yarn of Example 11 was more than twice that required to stretch the composite yarn of Example 12 to the same percentage elongation. Such a comparison indicates that the composite yarns having a core of a segmented elastomer also have a greater retractive force than the rubber core'yarns. This retractive force or power may be varied in the core-spun yarns disclosed herein by varying the elongation of the core above the front rolls.

The high-bulk, elastic core-spun y-arns of this invention are useful in woven, knitted, and non-woven fabrics for use in universal fitting apparel (socks, polo shirts, underwear, bathing suits, gloves, elastic cuffs, sweaters, waistbands, suits, coats, dresses, skirts, action sportwear, leotard-type outerwear, and accesories such as tapes, webbings and other woven, non-woven or knit apparel fabrics), household products (form-fitting upholstery, slip covers, sheets, carpets, mattress coverings, and narrow tapes and webbings for a wide variety of uses), industrial products (transportation upholstery, woven and non-woven felts, tapes and webbings for varied applications), and medical products (surgical bandages, supports,

elastic dressings, surgical stockings, and splint tapes). Such fabrics show an exceptionally even bulking of the yarn, which bulking takes place in the interstitial space be tween adjacent warp ends with practically no bulking under the Warp crossovers. This filling of the interstitial spaces with wedges of bulked sheath fibers gives a pleasant fulled appearance and handle to the fabric.

I claim:

1. A high-bulk elastic yarn comprising: an initially stretched elastic core including at least one straight, uncrimped, elastic filament and a sheath consisting of at least one staple fiber roving surrounding the core in a series of helical turns, said yarn having a core content of 'less than 40% by weight and a twist multiplier of less than about 4, said sheath and the fibers thereof being adapted to bulge outwardly when the core is permitted to contract.

2. The high-bulk yarn of claim 1 wherein said elastic core consists of a segmented elastomer in monofilament form.

3. The high-bulk yarn of claim 2 wherein the high-bulk yarn has a denier of less than about 300 in the relaxed state, the core content is from -40% by weight, and the twist multiplier is from 2-4.

4. The high-bulk yarn of claim 2 wherein the segmented elastomer has bis-ureylene segments alternating with segments of a low-melting polyether.

5. The high-bulk yarn of claim 1 wherein the twist multiplier is between 2 and 3.7 and the core content is from 1040% by weight.

6. A high-bulk, elastic yarn comprising: an initially stretched, straight, uncrimped filament of a segmented elastomer and a sheath consisting of at least two staple fiber rovings helically surrounding the filament, each roving being in engagement through the length thereof with the stretched filament and free of adhesion thereto, said yarn having'a filament content of from 10-30% by weight and a twist multiplier of from 2 to about 4, said sheath and individual fibers thereof being adapted to bulge outwardly when the yarn is permitted to contract.

7. The high-bulk yarn of claim 6 wherein the twist multiplier is less than 3.7.

8. A process of spinning high-bulk, elastic yarn comprising the steps of: drafting at least one roving of staple fibers; tensioning an elastic core including at least one straight uncrimped, elastic filament; gathering the roving and the core; and twisting the roving and core under 6 tension, using a twist multiplier between 2 and about 4 and limiting the core content to from 10-40% by weight.

9. The process of claim 8 wherein a twist multiplier of less than 3.7 is used.

10. The process of claim 8 wherein the elastic core is a monofilament of a segmented elastomer having bisureylene segments alternating with segments of a lowmelting polyether.

11. A process of spinning high-bulk elastic yarn comprising the steps of: drafting one or more rovings of staple fibers; gathering a straight, uncrimped, continuous elastic filament and the rovings; and twisting the gathered rovings and filament under tension, using a twist multiplier of less than 3.7 and limiting the filament content of the resulting yarn to less than 40% by weight.

12. A process of spinning high-bulk elastic yarn comprising the steps of: drafting one or more rovings of staple fibers; gathering a straight, uncrimped, continuous, elastic filament and the rovings; and twisting the gathered rovings and filament under tension, with the continuous filament substantially elongated and using a twist multiplier be tween 2 and -3.7.

13. A process of spinning high-bulk, elastic yarn comprising the steps of: drafting one or more rovings of staple fibers; tensioning a substantially twist-free elastic core; gathering the rovings and the core including at least one straight, uncrimped, elastic filament; and twisting the rovings and core, using a twist multiplier of less than about 4 and limiting the filament content of the resulting yarn to less than 40% by weight.

14. A fabric containing a high-bulk elastic yarn, said yarn comprising: a core including at least one straight, uncrimped, elastic filament and a sheath consisting of at least one staple fiber roving surrounding the core in a series of helical turns, said yarn having a core content of from 1040 by weight and a twist multiplier between 2 and about 4.

References Cited in the file of this patent UNITED STATES PATENTS 2,076,270 Harris Apr. 6, 1937 2,076,272 Harris Apr. 6, 1937 2,483,861 Weiss Oct. 4, 1949 2,813,775 Steuber Nov. 19, 1957 2,971,322 Bouvet Feb. 14, 1961 3,011,302 Rupprecht Dec. 5, 1961 

